1. Field of the Invention
The present invention relates to a method for setting up a QoS (Quality-of-Service) supported bi-directional tunnel and distributing L2VPN (Layer-2 Virtual Private Network) membership information for an L2VPN using an extended LDP (Label Distribution Protocol), wherein the method can more readily and efficiently manage L2VPN service and continuously provide better QoS in a customer network by extending the LDP to provide the L2VPN service.
2. Description of the Prior Art
MPLS (Multi Protocol Label Switching) is standard technology capable of improving the efficiency of a network and readily managing the network. In relation to an OSI (Open Systems Interconnection) basic reference model, the MPLS enables most packets to be transferred by Layer-2 switching rather than Layer-3 routing, enables traffic to be entirely distributed so that the traffic can be rapidly processed, and enables the network to readily be managed for better QoS (Quality-of-Service). For these reasons, the MPLS is expected to be adopted in a network for transmitting traffic data of various hybrid traffic types in the future.
The MPLS technology started from obtaining the scalability and flexibility of the Layer-3 routing and a higher performance and traffic management function of the Layer-2 switching by separating data forwarding and routing. Moreover, the MPLS technology is being standardized under the name of GMPLS (Generalized MPLS) as a generalized control component, which supports recently not only packet switching but also all of time-division switching, wavelength switching and fiber switching. As the MPLS/GMPLS technology provides various applications to control the Internet, more interest has been focused on the MPLS/GMPLS technology. Two representative applications are VPN (Virtual Private Network) service and traffic engineering service. Instead of service provided through a pre-existing leased line, the VPN service shares resources of a network of an SP (Service Provider), provides the scalability, stability, flexibility and security of the network, and connects sites associated with a plurality of private networks. More interest has been focused on the VPN service in that it provides high value-added service using the current Internet.
The MPLS/GMPLS technology is a standardized technology proposed to address a plurality of disadvantages associated with IP (Internet Protocol) technologies in the pre-existing Internet. Because the conventional IP technologies provide only best effort service through routing, they could not provide better QoS/CoS (Class-of-Service) required in transmitting current multimedia traffic data, that is, better QoS of a specific level. Further, in all the IP technologies, only the shortest routing path of all routing paths is first searched for according to a shortest path first rule. For this reason, the network could not be efficiently operated through the conventional IP technologies. Moreover, where a predetermined node or link of the network is failed, there is a problem in that the network cannot be stably operated because it takes much time to detect the failure through a routing protocol and bypass data to another path.
On the other hand, in comparison with the conventional IP technologies, the MPLS/GMPLS technology can efficiently employ the resources of the network by using the traffic engineering service, which can designate a specific router to each path. Moreover, there is an advantage in that the MPLS/GMPLS technology can support different QoS/CoS according to an LSP (Label Switched Path) being an MPLS/GMPLS path. Thus, the MPLS/GMPLS technology can provide high quality service differentiated from the conventional technology. Also, there is another advantage in that the traffic engineering service can be supported for the sake of the network efficiency. Furthermore, a bypass connection associated with each connection can be set in advance, against the failure of a specific node or link, thereby stably operating the network.
As the MPLS technology has more merits in comparison with the conventional IP technologies for use in the Internet, more interest and research is directed toward MPLS based VPN services in comparison with IP-based VPN services. IP tunneling-based VPN associated with basic VPN service has excellent security, but it is difficult to support better QoS in the IP tunneling-based VPN. Further, there is another disadvantage in that extension of the IP tunneling-based VPN is restricted due to a mesh structure and it is not easy to install and manage the IP tunneling-based VPN. On the other hand, the MPLS based VPN service has excellent extensibility and can support differentiated QoS. Moreover, there is another advantage in that the MPLS based VPN can easily manage services and an operating system in comparison with others.
ISPs (Internet Service Providers) for providing the VPN service can select two structures, which include an L2VPN (Layer-2 VPN) and an L3VPN (Layer-3 VPN). Their selections may be different according to technical support capabilities of edge equipment, i.e., a PE (Provider Edge), provided in the conventional ISPS. If the conventional PE has a routing protocol such as a BGP (Boarder Gateway Protocol) embedded therein and routing capability, it can easily provide the L3VPN service. Otherwise, if the conventional PE does not have the routing capability, it can easily provide the L2VPN service with low-cost equipment, which does not require the routing function. Where the VPN service is provided to transparently connect CE (Customer Edge) sites, which provide Layer-2 services such as an ATM (Asynchronous Transfer Mode), frame relay and Ethernet, a structure of the L2VPN is more appropriate.
Also, to distribute information associated with a VC (Virtual Circuit) connection being a connection between a PE and a CE to the remote PE, that is, to distribute L2VPN membership information between the PE and CE, a method for employing extension of a routing protocol such as the BGP or OSPF (Open Shortest Path First) has been proposed. However, this method needs the routing protocol embedded in the PE equipment by which the L2VPN service can be provided. The information distribution can be enabled through the extension of an LDP (Label Distribution Protocol), which can be used for a tunnel between PEs. The information distribution can be enabled by setting up a target session of the LDP and distributing a label for a VC connection. At this time, the routing protocol does not have to be necessarily mounted in the PE equipment.